In today's radio access network, a variety of vendors provide the radio access hardware. Unfortunately, the hardware tends to be completely interoperable only with products from the same manufacturer.
The use of common standards, including 3GPP standards, has been helpful in allowing interoperability. However, the standards are not always completely clear or completely specified. Also, since standards change slowly, manufacturers often add new features that are not supported by competitors' products.
Even common standards, such as X2, which permit exchange of arbitrary information between nodes, are not as useful as they could be because vendors are unwilling to expose functionality beyond what is minimally required.